1. Field of the Invention
This invention relates to binder compositions for fibrous mats and more particularly to a binder composition for fibrous mats, particularly of inorganic fibers such as glass fibers and/or mineral fibers, which is fire resistant when cured. The fibrous mats are useful for application in roofing and flooring products, for example, underlayment or facing for materials used in the building and construction industries.
2. Description of the Prior Art
Glass fiber mats and mineral wool fiber mats are composed of glass fibers and mineral wool fibers, respectively, held together by a binder material. Among other applications, such mats are treated to manufacture roofing felts for shingles and built-up roofing applications. Typical binders for glass fibers used by the industry are urea-formaldehyde, phenolic resins, bone glue, polyvinylalcohols, acrylic resins and polyvinyl acetates. See U.S. Pat. No. 4,258,098. Similarly thermosetting resins such as urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins are used to bind mineral wool fibers. See U.S. Pat. No. 3,215,585 (phenol-formaldehyde condensate-crystalline urea); and U.S. Pat. No. 4,542,068 (urea-formaldehyde with an alkoxylated alkyl amine surfactant).
The use of various combinations of aldehyde condensation polymers and latexes (lattices) have been proposed. U.S. Pat. No. 3,804,706 broadly discloses a binder composition containing a thermosetting resin such as urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins and a synthetic, water-insoluble, thermoplastic vinyl resin in an aqueous emulsion such as polyvinyl acetate, vinyl acetate-acrylonitrile copolymer, vinyl acrylate copolymer, vinyl acetate-ethyl acrylate copolymer, vinyl acetate-methylmethacrylate copolymer, and acrylic polymers. See also U.S. Pat. No. 4,637,951 (a heat settable polymer such as urea-formaldehyde and urea-formaldehyde and a latex such as an acetate or acrylic emulsion e.g. polyvinyl acetate); U.S. Pat. No. 4,255,485 (phenolformaldehyde-urea condensate with an emulsified thermoplastic resin e.g. vinylchloride polymer). A binder composition containing an urea-formaldehyde resin and a styrene-butadiene copolymer latex is disclosed in U.S. Pat. No. 4,258,098 (in combination with acrylamide-type monomer); U.S. Pat. No. 4,609,709 (in combination with a fully methylated melamine-formaldehyde copolymer); and U.S. Pat. No. 4,917,764 (narrow range of relative proportions and latex has a Tg &lt;25.degree. C.). In U.S. Pat. No. 4,255,485, an ethylene-vinylchloride emulsion polymer is used as the latex. In U.S. Pat. No. 4,609,709, the binder contains more latex than urea-formaldehyde thermosetting resin.
As these materials are utilized in building materials, there is a desire to improve the fire resistance of such materials. U.S. Pat. Nos. 3,470,977 (Shannon; acoustical board); U.S. Pat. No. 4,255,483 (Byrd et al.; fire barrier) and U.S. Pat. No. 4,457,969 (Biale; non-woven fabrics) relate to fire resistant fiber-composites. Colloidal silica is mentioned as an additive for improving fire resistance in U.S. Pat. No. 3,470,977 (Col. 2, lines 40-51) and in U.S. Pat. No. 4,255,483, in combination with a polyamide resin. U.S. Pat. No. 4,457,969 describes the fire resistance benefit attributable to latex polymers containing chloride. Latex polymers containing chloride in glass mat binder compositions are disclosed in U.S. Pat. No. 4,255,485 (Yau) without any mention of the fire resistance benefit attributable to such latexes.
The use of colloidal silica in binders for glass and minerals fibers is also known. See, for example, U.S. Pat. No. 2,886,466 (Ikler et al.) and U.S. Pat. No. 3, 077,413 (Campbell). U.S. Pat. No. 3,252,917 (Mindick et al.; Col. 12, lines 63-68) teaches the use of colloidal silica as a fire retardant.
U.S. Pat. No. 4,522,958 discloses a solvent based, organic, high solids coating composition containing a film-forming binder system containing a crosslinkable resin such as a thermosetting resin e.g. aminoplasts (etherified urea-formaldehyde and melamine-formaldehyde resins); a colorless, substantially inorganic microparticles stably dispersed in the coating composition (e.g. colloidal silicas which is optionally surface modified with carbon-containing molecules); and a solvent system. The coating may be used to coat fiber glass. There is no mention regarding the fire resistance benefit attributable to the use of colloidal silica.
However, the search continues for improved binder compositions for fibrous mats, particularly of inorganic fibers such as glass and/or mineral fibers, which are fire resistant when cured.